Apparatus, systems and methods for characterizing, imaging and/or modifying an object

ABSTRACT

Method and apparatus can be provided according to an exemplary embodiment of the present disclosure. For example, with at least one first section of an optical enclosure, it is possible to provide at least one first electro-magnetic radiation. In addition, with at least one second section provided within the enclosure, it is possible to cause, upon impact by the first radiation, a redirection of the first radiation to become at least one second radiation. Further, with at least one third section of the optical enclosure, it is possible to cause at least one second radiation to be provided to a tissue. For example, the redirection of the first radiation causes, at least approximately, a uniform optical illumination on of a surface of the tissue.

CROSS REFERENCE TO RELATED APPLICATION(S)

The present application relates to and claims priority from U.S.Provisional Patent Application Ser. No. 61/933,669 filed Jan. 30, 2014,the disclosure of which is incorporated herein by reference in itsentirety.

FIELD OF THE DISCLOSURE

Various exemplary embodiments of the present disclosure relate generallyto apparatus, systems and methods, which can characterize, image and/oror modify an object (e.g., tissue). In particular, various exemplaryembodiments of the present disclosure can relate to apparatus, systemsand methods for measuring photoacoustic signals. Further, variousexemplary embodiments of the present disclosure relate to apparatus,systems and methods which can facilitate a low-risk assessment ofcardiovascular function and diseases, such as, e.g., monitoringhemodynamic changes.

BACKGROUND INFORMATION

Use of light for characterizing, imaging and altering tissue has seendramatically expansion during the last decade. A challenge for designingan optical device can be how to make an efficient use of light togenerate a maximal diagnostic signal or treatment outcome. Further, manyoptical diagnosis and therapy are performed using endoscopes. Thepermissible optical fluence density on tissue surface can be regulatedby laser safety standards. Thus, it is likely preferable to enlargeand/or homogenize the illumination to admit more optical power. However,it can be difficult to achieve a sufficient large uniform illuminationarea from a compact endoscope following the current paradigm, which useslight guides, lenses and mirrors.

Photoacoustic imaging is a radiological technology, which generateshigh-definition volumetric images of tissue by measuring light-inducedsound waves—one or more photoacoustic signals—from its opticallyabsorbing structures. Through exciting various biomolecules at theircharacteristic absorption wavelengths, photoacoustic signals can be usedto analyze the molecular composition of a tissue at a clinicallyrelevant depth. For example, through exploiting the differentialabsorption spectra of oxy- and deoxy-hemoglobin, photoacoustic signal,measured from blood at a plurality of selected optical wavelengths, canbe used to evaluate local blood oxygenation of each individual bloodvessel, and provide information regarding cancer biology andcardiovascular diseases. When optimizing a photoacoustic system, a majorchallenge can be how to maximize photoacoustic generation using finiteoptical exposure allowed by established safety standards.

Hemodynamic monitoring plays an important role in managing criticallyill patients in emergency departments, surgical rooms and intensive careunits. Adequate blood oxygen supply to tissue can be essential tosustain human life. A lasting deficiency of tissue oxygen could lead tothe failure of vital organs, and is likely ultimately responsible formany deaths from a variety of diseases, such as, e.g., trauma, burn,heart attack and sepsis. Mixed venous oxygen saturation (SvO₂) is apreferred target of hemodynamic monitoring. SvO₂, the oxygen saturationmeasured from the mixed venous blood in a pulmonary artery, can reflecta dynamic balance between body's global oxygen supply and demand.Normally, SvO₂ is closely maintained between 60-80%. In patients, thereare various challenges to the balance of oxygen metabolism. For example,the oxygen demand can increase in case of fever, shivering and/orseizure, while the oxygen supply can decrease when bleeding. Whenchallenged, stable patients can restore the oxygen equilibrium byincreasing the cardiac output, and do not require hemodynamicintervention.

However, in high-risk patients, especially those with a poorcardiopulmonary reserve, a compensatory increase in cardiac output canbe limited. As a result, such patients have to call on bodies' last linedefense by extracting more oxygen from blood, i.e., when SvO₂ starts todecrease. For example, an immediate intervention can be indicatedif >10% deviation of SvO₂ from baseline is seen to last beyond, e.g., 3minutes. In current practice, SvO₂ can be measured with an indwellingpulmonary artery catheter (PAC), introduced invasively from a peripheralvein. The use of the PAC was found to be associated with about 10%incidence of complications, including hematoma, vessel puncture andcardiac arrest. As a result, the use of the PAC has been significantlydecreased, e.g., by 65% between 1993˜2004.

Accordingly, there may be a need to address and/or overcome at leastsome of the issues of deficiencies described herein above.

OBJECT AND SUMMARY OF EXEMPLARY EMBODIMENTS

To that end, apparatus, systems and methods according to certainexemplary embodiments of the present disclosure can be provided toovercome both aforementioned challenges by, e.g., increasinglight-tissue interaction, thereby be utilized in broad applications inoptical spectroscopy (e.g., scattering, fluorescence and Ramanspectroscopy, etc.), imaging (e.g., photoacoustic imaging, diffuseoptical tomography), or intervention (e.g., photodynamic, photothermalor low-level light therapy, etc.).

According to another exemplary embodiment of the present disclosure,apparatus, systems and methods for measuring a photoacoustic signal canbe provided. Such exemplary apparatus, systems and methods can beutilized for measuring the photoacoustic signals using alight-integrating enclosure, which can safely increase light absorptionin a targeted tissue, and generate a stronger photoacoustic signal forthe detection. In still another exemplary embodiment of the presentdisclosure, apparatus, low-risk systems and methods can be provided soas to facilitate monitoring of the oxygen metabolism, e.g., in criticalcare. In addition, exemplary transesophageal photoacoustic endoscope,system and method according to a further exemplary embodiment of thepresent disclosure can be provided, which can be used to measure thephotoacoustic signal from a pulmonary artery through a esophageal wall,and evaluate SvO₂ in, e.g., a less risky manner.

According to another exemplary embodiment of the present disclosure,apparatus, systems and methods can be provided to characterize, imageand/or modify tissue with light (or other electro-magnetic radiation),which can include a source generating light, an optical integratingenclosure that performs (a) redirecting the light or other radiation toilluminate a tissue and (b) increasing of an optical fluence on a tissuesurface. Such exemplary apparatus, systems and methods can be furtherconfigured to perform optical spectroscopy (e.g., scattering,fluorescence, Raman spectroscopy, etc.), imaging (e.g., photoacousticimaging, diffuse optical tomography, etc.), and/or a treatment (e.g.photodynamic, photothermal or low-level light therapy, etc.).

In yet a further exemplary embodiment of the present disclosure,apparatus, systems and methods can be provided to measure thephotoacoustic signal. For example, with a source, it is possible togenerate light or other electro-magnetic radiation with a time-varyingintensity. In addition, using an optical integrating enclosure, it ispossible to perform (a) redirecting of the light or other radiation toilluminate the tissue, and (b) increasing the optical fluence on thetissue surface. Further, with at least one acoustic transducer, it ispossible to detect acoustic signals generated from the illuminatedtissue volume.

According to yet another exemplary embodiment of the present disclosure,endoscopic apparatus, systems and methods can be provided for assessingcardiovascular functions or diseases, such as, e.g., monitoring a mixedvenous oxygen saturation. For example, using the source, it is possibleto generate light or other electro-magnetic radiation with atime-varying intensity. In addition, using an optical integratingenclosure, it is possible to redirect the light or the electro-magneticradiation to illuminate a pulmonary artery or other cardiac tissuethrough a wall of an esophagus. Further, with at least one acoustictransducer, it is possible to detect acoustic signals generated from thepulmonary artery, and with a computer processing arrangement or unit, itis possible to determine at least one property of the pulmonary arteryor other cardiac tissue.

Thus, method and apparatus can be provided according to an exemplaryembodiment of the present disclosure. For example, with at least onefirst section of an optical enclosure, it is possible to provide atleast one first electro-magnetic radiation. In addition, with at leastone second section provided within the enclosure, it is possible tocause, upon impact by the first radiation, a redirection of the firstradiation to become at least one second radiation. Further, with atleast one third section of the optical enclosure, it is possible tocause at least one second radiation to be provided to a tissue. Forexample, the redirection of the first radiation causes, at leastapproximately, a uniform optical illumination on of a surface of thetissue.

According to another exemplary embodiment of the present disclosure, thefirst section can have a cross-section that extends for a firstextension, and the second section can have a cross-section that extendsfor a second extension. The first extension can be smaller than thesecond extension. The enclosure can be structured such that when atleast one third radiation enters the enclosure from the tissue via thethird section, the third radiation is deflected at at least one fourthsection or at the second section within the enclosure, and forwardedback onto the surface of the tissue. The third radiation can be a returnradiation from the tissue associated with the second radiation.

In addition, according to yet further exemplary embodiment of thepresent disclosure, an acoustic detector arrangement can be providedwhich is configured to receive an acoustic wave information from thetissue. The acoustic wave can be generated within the tissue in responseto the second radiation provided on the tissue, the third radiationprovided from the tissue, and/or at least one fourth radiation providedfrom the enclosure that is a redirected radiation of the third radiationwithin the enclosure. The enclosure can be composed of at least onematerial that allows most or entirety of the acoustic wave from thetissue to penetrate at least most of the enclosure. The enclosure can beprovided in an approximate contact with the acoustic detector. Further,an acoustic matching layer can be provided between the acoustic detectorand the enclosure.

According to still another exemplary embodiment, the first portionand/or the third portion can have a curvature that facilitates (i) auniform distribution or (ii) a large area of illumination of at leastone of the second radiation provided on the tissue, the third radiationprovided from the tissue, and/or at least one fourth radiation providedfrom the enclosure that is a redirected radiation of the third radiationwithin the enclosure. The enclosure can have a shape of an acousticlens. The second section can be (i) composed of a scattering materialand/or (ii) have a scattering coating thereon, to effectuate theredirection of the first radiation. The scattering material can includea combination of an optically-transparent silicon rubber with lightscattering particles. The enclosure can also comprise at least onefourth section through which the first radiation travels to reach thesecond section, where the fourth section can be approximatelytransparent. The transparent fourth section can be composed at least inpart of silicon rubber, which can be substantially opticallytransparent.

In yet a further exemplary embodiment of the present disclosure, atleast one fiber arrangement can be provided which can facilitate thereonor therethrough the first radiation. Further, an acoustical detector canbe provided which is configured to receive an acoustic radiation fromthe tissue based on at least one of the second radiation provided on thetissue, the third radiation provided from the tissue, and/or at leastone fourth radiation provided from the enclosure that is a redirectedradiation of the third radiation within the enclosure. The enclosure,the fiber arrangement and the detector can be provided in a probe. Thefiber arrangement can have a distal end in a proximity of the enclosurethat has a curved shape to facilitate (i) a uniform distribution or (ii)a large area of illumination of the second radiation provided on thetissue, the third radiation provided from the tissue, and/or at leastone fourth radiation provided from the enclosure that is a redirectedradiation of the third radiation within the enclosure.

These and other objects, features and advantages of the exemplaryembodiments of the present disclosure will become apparent upon readingthe following detailed description of the exemplary embodiments of thepresent disclosure, when taken in conjunction with the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects, features and advantages of the present disclosure willbecome apparent from the following detailed description taken inconjunction with the accompanying figures showing illustrativeembodiments of the present disclosure, in which:

FIG. 1 is a cross-sectional side-view diagram of an optical apparatusaccording to an exemplary embodiment of the present disclosure;

FIG. 2 is a cross-sectional side-view diagram of a photoacousticmeasuring apparatus according to an exemplary embodiment of the presentdisclosure;

FIG. 3 is a diagram of a transesophageal photoacoustic endoscopic systemfor monitoring a mixed venous oxygen saturation, according to anexemplary embodiment of the present disclosure;

FIG. 4 is an exemplary wide-field optical illumination on tissue surfaceachieved by one exemplary embodiment of the apparatus, systems andmethods according to the present invention illustrated in FIG. 3; and

FIG. 5 is a graph illustrating a mixed venous oxygenation changes overtime in response to varying fraction of inspired oxygen, evaluated bythe transesophageal photoacoustic endoscope, according to the exemplaryembodiment of the present disclosure illustrated in FIG. 3.

Throughout the figures, the same reference numerals and characters,unless otherwise stated, are used to denote like features, elements,components or portions of the illustrated embodiments. Moreover, whilethe subject disclosure will now be described in detail with reference tothe figures, it is done so in connection with the illustrativeembodiments. It is intended that changes and modifications can be madeto the described exemplary embodiments without departing from the truescope and spirit of the subject disclosure as defined by the appendedclaims.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 illustrates a cross-sectional view of an exemplary apparatus thatincludes an optical enclosure 110 according to one exemplary embodimentof the present disclosure. For example, light 102 (or otherelectro-magnetic radiation) can be delivered by the enclosure 110 tocharacterize, image and/or modify a targeted object 152 in a tissue 150.The enclosure 110 can include a light-transporting medium 112, alight-redirecting coating 114, an input port 116, and/or an output port118. The light 102 (or other electro-magnetic radiation) can be providedinto said the enclosure 110 via the input port 116, and exit to impact asurface of the tissue 150 through the output port 118. Thelight-transporting medium 112 can be composed of a material with a lowoptical absorption, such as, e.g., air, water, saline, oil, clearrubber, plastic and/or gel. The light-transporting medium 112 can alsocontain a small amount of optical scatters (e.g., <5% weight ratio),such as, e.g., titanium dioxide, hafnium oxide, zinc oxide, ytterbiumoxide or hafnium oxide particles.

The medium 112 can be surrounded by a light-redirecting coating 114,except at the input port 116 and/or the output port 118. The coating 114can have a high optical reflectance, e.g., close to unity, and/or anear-Lambertian optical scattering phase function. The coating 114 canbe composed of commercially available high diffusive reflectancematerial, such as, e.g., Spectralon, Spectraflect and/or Permaflect(Labsphere), and Avian-B or Avian-D white paint (Avian Technologies).Alternatively or in addition, the light-redirecting coating 114 can alsobe made by doping a medium with light scattering particles, such as,e.g., titanium dioxide, hafnium oxide, zinc oxide, ytterbium oxideand/or hafnium oxide, at a high concentration (e.g., >20% weight ratio).The coating 114 can also have a partial and/or high specularreflectance. After entering the enclosure 110, most of the light 102 orother electro-magnetic radiation can bounce around the enclosure 110,impact one or more surfaces of the coating 114, thereby becomehomogenized inside the medium 112. Such light 102 or radiation can onlyexits through either the output port 118 or the input port 116. In oneexemplary embodiment, the output port 118 can have a larger area thanthe input port 116. Therefore, the optical enclosure 110 can redirectand/or expand most of the light 102 or other radiation to create auniform wide-area illumination on a surface of the tissue 150 throughthe output port 118. Since a maximal permissible optical fluence densityon the tissue surface is generally regulated by established safetystandards, by enlarging and/or homogenizing the illumination, theenclosure 110 facilitates a delivery of a larger amount of opticalenergy onto the tissue 150. As an exemplary result, the interactionbetween the light 102 (or other radiation) and the target 152 can beincreased. The input port 116 and/or the output port 118 can further beconfigured, shaped or constructed to have a desired curvature, e.g., inorder to shape the light 102 (or other radiation) at the entrance and/orthe exit to further homogenize and/or expand the illumination.

Furthermore, the enclosure 110 can be designed and/or modified to make amore efficient use of the same amount of the input light. Since thebiological tissue is highly scattering to light, a significant portionof the light 102 (or other electro-magnetic radiation), which originallyexits from the output port 118, is backscattered out from the tissue150. The enclosure 110 can have a configuration to capture there-emitted portion of the light 102 (through the input port 116 and/orthe output port 118), send such light 102 (or other radiation) backthrough the output port 118 onto a surface of the tissue 150, so as tofurther increase the chance or an actuality of the interaction betweenthe light 102 and the target 152. Therefore, the optical enclosure 110can be used to further enhance a light-tissue interaction in variousoptical modalities, such as spectroscopies (e.g., scattering,fluorescence, Raman spectroscopy, etc.), imaging (e.g., photoacousticimaging, diffuse optical tomography, etc.), or treatment (e.g.,photodynamic, photothermal, low-level light therapy, etc.). Further,e.g., in order to obtain a uniform large-area optical illumination, theoptical enclosure 110 can be shaped and or provided in a smaller size,e.g., when compared to other light-redirecting apparatus or systems thatuse only light guides, lenses or mirrors. Therefore, the exemplaryenclosure 110 can be used in an optical endoscope system.

FIG. 2 illustrates a cross-sectional side-view diagram of aphotoacoustic apparatus or device 200 according to an exemplaryembodiment of the present disclosure. The exemplary photoacoustic device200 can illuminate the tissue with light 202 or other electro-magneticradiation, induce emission of an acoustic wave 206 from an opticallyabsorbing object 252, such as, e.g., a blood vessel, within a tissue250, record the light-induced sound remotely by an acoustic detector220, and obtain information regarding the tissue by analyzing orreconstructing the recorded signals. The light 202 (or other radiation)can have a time-varying intensity. Examples of the acoustic detector 220can include, but are not limited to, a microphone, a hydrophone, apiezoelectric transducer, a polyvinylidene fluoride film transducer, acapacitor micro-machined transducer, an optical acoustic sensor based onlight interferometry, etc. The acoustic detector 220 can also be orinclude a combination of a plurality of aforementioned acousticdetectors, such as a phased array acoustic probe, etc. For example, acentral frequency of the acoustic detector can preferably be in therange of about or exactly 0.5˜100 MHz.

According to one exemplary embodiment of the present disclosure, thelight 202 (or other radiation) can be delivered to the tissue 250through a light-integrating enclosure 210. The light-integratingenclosure 210 can include a light-transporting medium 212, alight-redirecting coating 214, an input port 216, and an output port218, etc. The medium 212 can be made of a material with a low lightabsorption, such as, e.g., air, water, oil, clear rubber, plastic and/orgel, etc. The medium 212 can be surrounded by the light-redirectingcoating 214, e.g., except at the input port 216 and/or the output port218. The coating 214 can have a high optical reflectance close to, e.g.,unity and/or a near-Lambertian optical scattering phase distribution.The coating 214 can be composed of a commercially available high opticaldiffusive reflectance material, such as, e.g., Spectralon, Spectraflector Permaflect (Labsphere), and Avian-B or Avian-D white paint (AvianTechnologies). Alternatively or in addition, the light-redirectingcoating 214 can also be made by doping a optically clear medium withlight scattering particles, such as, e.g., titanium dioxide, hafniumoxide, zinc oxide, ytterbium oxide or hafnium oxide, at a highconcentration (e.g. >20% weight ratio). As elaborated above, compared toa conventional photoacoustic device that utilizes a side illumination,the photoacoustic device 200 using a light-integrating enclosure 210 canproduce a uniform illumination over a large surface of the tissue 250,thereby facilitate a use of more total optical energy, a re-use of theback-scattered light from tissue and an increase of the optical energyabsorbed by the object 252, thereby boost the photoacoustic signalreaching the acoustic detector 220.

According to another exemplary embodiment of the present disclosure, themedium 212 and/or the light-redirecting coating 214 can further be madeof a material having a low acoustic attenuation. Thus, thelight-integrating enclosure 210 can act as an acoustic lens, and can beattached to the acoustic detector 220. Most of the acoustic wave 206 canbe propagated through the light-integrating acoustic lens 210 to reachthe acoustic detector 220. The low-acoustic-attenuationlight-transporting medium 212 can be made of water, oil, poly(methylmethacrylate) (e.g., Arylic), polystyrene (e.g., Rexolite1422, C-lecPlastics), polymethylpentene (e.g., DX845, Mitsui Chemical),polyurethane, silicone rubber (e.g., RTV615, Momentive). Thelow-acoustic-attenuation light-redirecting coating can be made orotherwise generated by doping a medium, similar to that used to make themedium 212, with light scattering particles, such as, e.g., titaniumdioxide, hafnium oxide, zinc oxide, ytterbium oxide or hafnium oxide, ata high concentration (e.g., >20% weight ratio). Furthermore, an acousticmatching layer 222 can be placed between the acoustic lens 210 and theacoustic detector 220, e.g., to reduce an acoustic loss due to thereflection. In addition or as an alternative, the lens 210 can be madeof a material with a different acoustic speed than that of the tissue250. To that end, the lens 210 can be shaped to diverge or converge theincoming acoustic wave 206, thereby facilitating a zoom-in or wide-angleview inside the tissue 250.

FIG. 3 illustrates a transesophageal photoacoustic endoscope system 300according to another exemplary embodiment of the present disclosure. Theexemplary system 300 can comprise an optical light source 330, atransesophageal probe (e.g., including a flexible shaft 340 and aninflexible in-esophagus head 342), an acoustic puller/receiver 332, aprocessor 336 and a graphic user interface 338. The flexible shaft 340can contain a segment of a light guide 322 and an electric cable 324.The inflexible head 342 can include a distal end of the light guide 322,a light-integrating acoustic lens 310 described herein, and an acoustictransducer 320. Either or both of the probe head 342 and the shaft 340can have a diameter smaller than 15 mm, thereby facilitating anintroduction thereof into the esophagus 308 through a mouth or a nose.Such exemplary system can be used to safely assess cardiovasculardiseases and/or functions. For example, such exemplary system can beutilized to monitor mixed venous oxygen saturation (SvO₂) from apulmonary artery 352 through a wall of an esophagus 350. Other examplesof using such exemplary system include diagnosing atherosclerosis,assessing myocardial diseases, evaluating cardiac defects, guidingatrial ablation, etc.

The optical source 330 can generate a light 302 (or otherelectro-magnetic radiation) with a time-varying intensity. The light 302(or other radiation) can have (but not limited to) a wavelength between,e.g., 600 and 1800 nm. The light source 330 can be or include a pulsedlaser, such as a Q-switched Nd:YAG laser, a fiber laser, a dye laser, aTi-sapphire laser, an OPO laser, or a pulsed diode laser. The pulseduration of the light 302 can be (but not limited to) at the order ofnanoseconds. The source 330 can also be or include anintensity-modulated continuous-wave light source, such as a laser diode,a LED or a solid-state laser. The light guide 322 can be used to carrythe light 302 from the source 330 into the head 342. Examples of suchlight guide 322 include, but are not limited to a borosilicate orsilica/silica fiber bundle, a photonic crystal fiber, an articulated armwith mirrors or prisms, etc. The middle segment of the light guide 322can be included inside the shaft, can contain loose fibers and beflexible. The light guide 322 can have inflexible segments close to atleast one of the proximal end and the distal end, by fusing, gluing oradding a rigid housing to optical fiber(s). The light 302, generated bythe optical source 330, can be focused by optical lenses into theproximal end of the light guide 322, exit from a distal end of saidlight guide 322, and provide the light 302 to the light-integratingacoustic lens 310. Then, the light 302 can be redirected to form auniform wide-field illumination on a surface of the esophagus 350. Thedistal end of the light guide 322 can further be polished into a shape,which can deflect, reflect or diverge the light 302 to so as to achievea large uniform optical illumination on the tissue.

According to an exemplary embodiment of the present, photoacousticmeasurements can be made with the light at a plurality of wavelengths toevaluate a blood oxygen saturation, e.g., using one or more componentsdescribed herein. For example, the source 330 can be tuned to generatethe light with a plurality of wavelengths. In addition or alternatively,the source 330 can be or include a combination of a plurality of opticalsources that can operate at distinct wavelengths. In addition, the shaft340 and the head 342 can be configured, structured and/or sized to benavigated to characterize different tissue through the esophageal wallby advancing, rotating or flexing the drive shaft 340. In addition, theacoustic detector 320 can be rotated inside the probe head 340 to viewthe tissue in a view plane of interest. For an exemplary evaluation ofSvO₂, as depicted in FIG. 3, a user can navigate the probe head 342inside the esophagus 350 to obtain an appropriate good view of thepulmonary artery 352. After absorbing part of the light 302, the mixedvenous blood inside a pulmonary artery 304 can emit an acoustic wave306, which can be converted by an acoustic detector 320 into electricalsignal. The electric signal can be carried by an electrical cable 324into the acoustic pulser/receiver 332, where such electrical signal canbe amplified, filtered and/or digitized. The digital samples of suchsignals can then be analyzed by a computer processor 334 to calculate orotherwise determine SvO₂ and analyze results, which can be providedthereby on a graphic interface 336. In addition, the pulser/receiver 332can also be configured to transmit, e.g., a high-voltage electricalsignal through the cable 324 to energize the acoustic transducer 320 toemit an acoustic wave (not shown). By detecting the reflected acousticwaves from tissue, real-time sonographic images 338 depicting tissueanatomy can be obtained and/or provided to guide a rapid deployment ofthe probe head 342.

FIG. 4 shows a wide-field optical illumination on tissue surfaceachieved by the embodiment of the transesophageal photoacousticendoscopic system according to the present disclosure illustrated inFIG. 3. For example, since the optical fluence density on tissue surfaceis regulated by laser safety standards, a wide-field illuminationfacilitates the use of more light to generate a higher photoacousticsignal. Simulation shows that, compared to a conventional photoacousticendoscope where light is illuminated from a side of the acousticdetector, the exemplary transesophageal photoacoustic endoscopic systemillustrated in FIG. 3 can produce more than twice of a photoacousticemission. As shown in FIG. 4, a homogenous 13 mm-diameter illuminationis obtained by the light-integrating acoustic lens 310 of a thickness ofonly 3 mm, which demonstrates the exemplary embodiments of the presentdisclosure can be useful for making compact endoscopes.

FIG. 5 shows a time profile of mixed venous oxygenation evaluated by thetransesophageal photoacoustic endoscope according to the exemplaryembodiment of the present disclosure. For example, blood can becirculated inside extracorporeal cardiopulmonary bypass circuit. Bloodoxygen content can be modulated by varying the fraction of oxygen in thegas, which the blood breathes. The photoacoustic signals were measuredfrom blood at two selected near-infrared wavelengths. The real-timeoxygen saturation is estimated in the illustration of FIG. 4 based onthe ratio of the two photoacoustic signals.

The foregoing merely illustrates the principles of the disclosure.Various modifications and alterations to the described embodiments willbe apparent to those skilled in the art in view of the teachings herein.It will thus be appreciated that those skilled in the art will be ableto devise numerous systems, arrangements and methods which, although notexplicitly shown or described herein, embody the principles of thedisclosure and are thus within the spirit and scope of the presentdisclosure. Further, the exemplary embodiments described herein canoperate together with one another and interchangeably therewith. Inaddition, to the extent that the prior art knowledge has not beenexplicitly incorporated by reference herein above, it is explicitlybeing incorporated herein in its entirety. All publications referencedherein above are incorporated herein by reference in their entireties.

What is claimed is:
 1. An apparatus, comprising: an optical enclosureincludes (i) at least one first section that facilitate at transmissiontherethrough of at least one first electro-magnetic radiation, (ii) atleast one second section within the optical enclosure that, upon impactby the first radiation, redirects the first radiation to become at leastone second radiation, and (iii) at least one third section which isconfigured to provide at least one second radiation to a tissue, whereinthe redirection of the first radiation causes, at least approximately, auniform optical illumination on of a surface of the tissue.
 2. Theapparatus according to claim 1, wherein the first section has across-section that extends for a first extension, and the second sectionhas a cross-section that extends for a second extension, and wherein thefirst extension is smaller than the second extension.
 3. The apparatusaccording to claim 1, wherein the enclosure is structured such that whenat least one third radiation enters the enclosure from the tissue viathe third section, the third radiation is deflected at at least onefourth section or at the second section within the enclosure, andforwarded back onto the surface of the tissue, and wherein the thirdradiation is a return radiation from the tissue associated with thesecond radiation.
 4. The apparatus according to claim 1, furthercomprising an acoustic detector arrangement which is configured toreceive an acoustic wave information from the tissue, wherein theacoustic wave is generated within the tissue in response to at least oneof the second radiation provided to the tissue, the third radiationprovided from the tissue, or at least one fourth radiation provided fromthe enclosure that is a redirected radiation of the third radiationwithin the enclosure.
 5. The apparatus according to claim 4, wherein theenclosure is composed of at least one material that allows most orentirety of the acoustic wave from the tissue to penetrate at least mostof the enclosure.
 6. The apparatus according to claim 4, wherein theenclosure is provided in an approximate contact with the acousticdetector.
 7. The apparatus according to claim 6, further comprising anacoustic matching layer provided between the acoustic detector and theenclosure.
 8. The apparatus according to claim 1, wherein at least oneof the first portion or the third portion has a curvature thatfacilitates (i) a uniform distribution or (ii) a large area ofillumination of at least one of the second radiation provided on thetissue, the third radiation provided from the tissue, or at least onefourth radiation provided from the enclosure that is a redirectedradiation of the third radiation within the enclosure.
 9. The apparatusaccording to claim 1, wherein the enclosure has a shape of an acousticlens.
 10. The apparatus according to claim 1, wherein the second sectionat least one of (i) composed of a scattering material or (ii) has ascattering coating thereon, to effectuate the redirection of the firstradiation.
 11. The apparatus according to claim 10, wherein thescattering material includes a combination of an optically-transparentsilicon rubber with light scattering particles.
 12. The apparatusaccording to claim 10, wherein the enclosure comprises at least onefourth section through which the first radiation travels to reach thesecond section, wherein the fourth section is approximately transparent.13. The apparatus according to claim 12, wherein the transparent fourthsection is composed at least in part of silicon rubber, which issubstantially optically transparent.
 14. The apparatus according toclaim 1, further comprising: at least one fiber arrangement providingthe first radiation; and an acoustical detector which is configured toreceive an acoustic radiation from the tissue based on at least one ofthe second radiation provided on the tissue, the third radiationprovided from the tissue, or at least one fourth radiation provided fromthe enclosure that is a redirected radiation of the third radiationwithin the enclosure, wherein the enclosure, the fiber arrangement andthe detector are provided in a probe.
 15. The apparatus according toclaim 14, wherein the fiber arrangement has a distal end in a proximityof the enclosure that has a curved shape to facilitate (i) a uniformdistribution or (ii) a large area of illumination of at least one of thesecond radiation provided on the tissue, the third radiation providedfrom the tissue, or at least one fourth radiation provided from theenclosure that is a redirected radiation of the third radiation withinthe enclosure.
 16. A method, comprising: with at least one first sectionof an optical enclosure, providing at least one first electro-magneticradiation, with at least one second section within the opticalenclosure, causing, upon impact by the first radiation, a redirection ofthe first radiation to become at least one second radiation; and with atleast one third section of the optical enclosure, causing at least onesecond radiation to be provided to a tissue, wherein the redirection ofthe first radiation causes, at least approximately, a uniform opticalillumination on of a surface of the tissue.